A new study published in Stroke: Journal of the American Heart Association found that women who drank more than one cup of coffee a day had about a 25 percent lower risk of stroke than women who drank less than that.

"More research is needed before implications for public health can be considered," Susanna Larsson, lead author of the study and a researcher in the division of nutritional epidemiology at the National Institute of Environmental Science in Stockholm, Sweden, told ABCNews.com. But at least coffee does not seem to cause harm, she said.

In 1997, researchers enrolled more than 34,000 women between the ages of 49 and 83 who were free of heart disease in the study, and followed them for about 10 years, concluding that coffee consumption may be linked to reduced stroke risk, cerebral infarction and subarachnoid hemorrhage in women.

According to the American Heart Association, stroke is the third largest cause of death in the United States, and it is the leading cause of serious, long-term disability.

As one of the most popular drinks in the world, coffee has been subjected to several studies, but the data from studies on coffee and stroke risk in the past decade have been conflicting.

A study published in Circulation in February 2009 found that women who drank four or more cups of coffee a day reduced their risk of stroke by 20 percent. But another study published in the journal Neurology in November 2010 found that stroke risk increased in the hour after drinking coffee but reversed itself within two hours.

Studies of Association, Not Causation

Doctors said Larsson's study is just one more piece of research to throw into the discussion, and is not the last word.

"All of these are studies of association, and do not prove that drinking coffee prevents stroke," said Dr. Larry Goldstein, a professor of medicine at Duke University and director of the Duke Stroke Center. "No study is definitive, and that's why people have to be careful when reacting to individual studies."

Goldstein said it is important to keep in mind that even when controlled, there are still several unmeasured factors that could be important in the study's final outcome, including other lifestyle and behavioral choices.

Because the study was done in Sweden, Goldstein said the results could be very different for those living in a multiethnic society like the United States.

"From a scientific standpoint, these studies are important because they provide clues and give us things to look into," said Goldstein. "But they have to be considered in context with all of their limitations.

"A positive is that there certainly didn't appear to be an increased risk with coffee drinking," said Goldstein. "But you may not be able to say that somewhere else."

Dr. Cathy A. Sila, director of the Stroke and Cerebrovascular Center at Case Western Reserve University School of Medicine, said retrospective dietary and nutritional studies can be a challenge to interpret.
While the rate of stroke in the 10-year study period is likely to be quite accurate, Sila said the self-reported questionnaire is likely to be riddled with bias and inaccuracy.

"How do we even know that their self-estimated consumption was accurate?" asked Sila. "Why was there a no dose-response? If one cup is better, shouldn't five cups be amazing? How do we know that they were still doing in 1998 to 2008 was what they were doing in 1997?"

Stick to the Tried and True

While Sila did not deny coffee's possible ability to reduce stroke risk, there are several other major and more scientifically backed factors that contribute to stroke prevention.

"The 'big ticket items' for stroke prevention are the real story," said Sila. "High blood pressure is the most important risk factor for stroke and has been called the silent killer."

Sila said most people in the United States don't know they have high blood pressure or are not at their blood pressure goal, or know they have it but don't do anything about it.

Sticking to the tried and true is what really counts in reducing the risk of stroke, say medical experts.

A diet rich in fruits and vegetables, low in sodium and high in potassium, said Goldstein, "can dramatically reduce risk," along with "not smoking and not being exposed to secondhand smoke, not drinking in excess, regular exercise and keeping a lean body mass."